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                <h1>Fun with Strings</h1>

                <p class="post-footer align-right">
                  <strong>
                    <a href="/satishtalim/numbers_in_ruby.html">&lt;Numbers | </a>
                    <a href="/satishtalim/tutorial.html">TOC | </a>
                    <a href="/satishtalim/variables_and_assignment.html">Variables and Assignment&gt;</a>
                  </strong>
                </p>

                <p>
                  String literals are sequences of characters between single or
                  double quotation marks.
                </p>

                <p>
                  '' (ie. two single quotes) does not have anything in it at
                  all; we call that an empty string.
                </p>

                <p>
                  Here's a program <strong>p003rubystrings.rb</strong> that
                  explores strings to some extent:
                </p>

                <div class="column2">
                <!-- InstanceBeginEditable name="Code" -->
                <textarea name="code" class="ruby:nogutter:nocontrols" rows="15" cols="60">
                # p003rubystrings.rb
                =begin
                  Ruby Strings
                  In Ruby, strings are, by default, mutable
                =end

                puts "Hello World"
                # Can use " or ' for Strings, but ' is more efficient
                puts 'Hello World'
                # String concatenation
                puts 'I like' + ' Ruby'
                # Escape sequence
                puts 'It\'s my Ruby'
                # New here, displays the string three times
                puts 'Hello' * 3
                # Defining a constant
                # More on Constants later, here
                # /satishtalim/ruby_names.html
                PI = 3.1416
                puts PI
                </textarea>
                <!-- InstanceEndEditable -->
                </div>

                <p class="post-note">
                  a. If <strong>puts</strong> is passed an
                  object that is not a string, <strong>puts</strong> calls the
                  <strong>to_s</strong> method of that object and prints the
                  string returned by that method.<br />
                  b. In Ruby, strings are <strong>mutable</strong>. They
                  can expand as needed, without using much time and memory. Ruby
                  stores a string as a sequence of characters.<br />
                  c. Introduced in Ruby 2.3, the magic string of <code>#
                  frozen_string_literal: true</code> will freeze literal
                  strings, allowing specific strings to be mutable by prepending
                  a <code>+</code> directly before the opening string delimiter.
                  Using <code>.dup</code> on a string will allow the cloned
                  string to be mutable as well, allowing for benefits from
                  mutating strings, when that makes sense to do so.
                </p>

                <p>It's worth knowing that a special kind of string exists that
                  uses the back-tick (`) or Grave accent as called in the US, as
                  a beginning and ending delimiter. For example:
                </p>

                <div class="column2">
                <!-- InstanceBeginEditable name="Code" -->
                <textarea name="code" class="ruby:nogutter:nocontrols" rows="15" cols="60">
                puts `dir`
                </textarea>
                <!-- InstanceEndEditable -->
                </div>

                <p>The command output string is sent to the operating system as
                  a command to be executed (under windows operating system, we
                  have sent the dir command), whereupon the output of the
                  command (dir on a command window would display all the files
                  and sub directories in your folder) is then displayed by
                  <strong>puts</strong>.
                </p>

                <p>On Linux and Mac, you can instead do:</p>

                <div class="column2">
                <!-- InstanceBeginEditable name="Code" -->
                <textarea name="code" class="ruby:nogutter:nocontrols" rows="15" cols="60">
                puts `ls`
                </textarea>
                <!-- InstanceEndEditable -->
                </div>

                <p>Another way to spawn a separate process is to use the
                  <strong>Kernel</strong> method <strong>system</strong>. The
                  method executes the given command in a sub-process; it returns
                  <strong>true</strong> if the command was found and executed
                  properly. It returns <strong>false</strong> if command exited
                  with a nonzero exit status, and <b>nil</b> if the command
                  failed to execute. Remember, the command's output will simply
                  go to the same destination as your program's output.
                </p>

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                <!-- InstanceBeginEditable name="Code" -->
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                system("tar xzf test.tgz") # => true
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                <p style="background-color: #FAFAFA; padding: 5px; margin-top: 20px; font-size: 65%;"><strong>Note</strong>: The Ruby Logo is Copyright (c) 2006, Yukihiro Matsumoto. I have made extensive references to information, related to Ruby, available in the public domain (wikis and the blogs, articles of various <span style="font-weight: bold;" title="Click Gurus on the menu above">Ruby Gurus</span>), my acknowledgment and thanks to all of them. Much of the material on <a href="/">rubylearning.github.io</a> and in the course at <a href="http://rubylearning.org/">rubylearning.org</a> is drawn <strong>primarily</strong> from the <strong>Programming Ruby book</strong>, available from <a href="https://pragprog.com/book/ruby4/programming-ruby-1-9-2-0">The Pragmatic Bookshelf</a>.</p>

                <p class="post-footer align-right">
                  <strong>
                    <a href="/satishtalim/numbers_in_ruby.html">&lt;Numbers | </a>
                    <a href="/satishtalim/tutorial.html">TOC | </a>
                    <a href="/satishtalim/variables_and_assignment.html">Variables and Assignment&gt;</a>
                  </strong>
                </p>

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